1. Field of the Invention
The present invention relates to a liquid ejecting recording head for performing a recording operation by discharging a recording liquid from a small discharging port as a liquid droplet and attaching this recording liquid to a recorded medium such as recording paper, etc. in a liquid ejecting recording system, and particularly, relates to a liquid ejecting recording head capable of stably discharging the recording liquid droplet at high speed to form a high definition image.
2. Related Background Art
As described in Japanese Patent Application Laid-Open No. 55-132253, a conventional general liquid ejecting recording head is constructed by joining first and second substrates to each other. A discharging energy generating element for discharging a recording liquid is formed in the first substrate. The second substrate has a discharging port for discharging the recording liquid, a liquid flow path groove communicated with the discharging port, and a common liquid chamber for supplying the recording liquid to this liquid flow path groove. The first and second substrates are joined to each other in a form in which the discharging energy generating element and the flow path groove correspond to each other.
Japanese Patent Application Laid-Open No. 2-192954 discloses a liquid ejecting recording head having first and second substrates. A discharging energy generating element is formed in the first substrate. A common liquid chamber and plural liquid flow path grooves having an opening portion as a discharging port from this common liquid chamber are formed in the second substrate. The first and second substrates are more reliably joined to each other by a mechanical biasing force.
Further, in a method introduced in Japanese Patent Application Laid-Open No. 4-171128, a position of the discharging energy generating element of the first substrate and a position of the discharging port of the second substrate are respectively measured to accurately join the first and second substrates. Measured values of these positions are compared with each other, and the second and first substrates are relatively moved by a difference between these measured values so that the positions of the discharging energy generating element and the discharging port are aligned with each other.
Further, Japanese Patent Application Laid-Open Nos. 7-148944 and 7-148926, etc. propose a compact liquid ejecting recording head for color. In this liquid ejecting recording head for color, a second substrate has a discharging port for discharging a recording liquid, a liquid flow path groove communicated with the discharging port, and a common liquid chamber for supplying the recording liquid to this liquid flow path groove. In this second substrate, the common liquid chamber is divided into plural chambers and a recording liquid of a different color is supplied for each of the plural chambers.
FIG. 7 is an exploded perspective view showing the construction of the conventional general liquid ejecting recording head. In this figure, reference numeral 111 designates a first substrate in which a discharging energy generating element 111a is formed. This first substrate 111 is fixed to a base plate 112 together with a wiring substrate 113 for transmitting an electric signal. A second substrate 114 has plural concave portions for constructing plural common liquid chambers, plural liquid flow path grooves, and plural discharging ports 114a for discharging a recording liquid. A pressing member 115 such as a spring, etc. presses against the first substrate 111 and is joined to this first substrate 111 by giving a mechanical biasing force to the second substrate 114.
Positions of both the substrates are aligned with each other and these substrates are joined to each other such that the discharging energy generating element 111a of the first substrate 111 and the discharging ports 114a and the liquid flow path grooves of the second substrate 114 correspond to each other. The biasing pressing force of the pressing member 115 is given to an upper face of the second substrate 114, particularly, to an upper portion of a forming portion of the liquid flow path grooves of the second substrate 114 so that joining faces of the first and second substrates 111, 114 are closely attached to each other.
In the liquid ejecting recording head, the second substrate is large-sized to obtain a higher definition image for a short time when the number of liquid flow paths, i.e., the number of nozzles, is increased. As a result, the joining of the first and second substrates becomes insufficient so that it is very difficult to obtain an adequate image. As a general countermeasure for coping with such a situation, there is a method for increasing a resilient pressure of the spring member as the mechanical biasing force. However, in this method, this pressure is too strong and pressure concentration is caused so that the second substrate is excessively deformed. Further, this deformation is also transmitted to an orifice plate and causes deformation of the discharging ports, etc. When such deformation of the discharging ports is caused, the reaching position of a recording liquid droplet is shifted so that no sufficient image can be instantly obtained.
When no sufficient joining of the first and second substrates is obtained, a gap is caused between the first substrate and each liquid flow path groove of the second substrate. Therefore, pressure generated by the discharging energy generating element is dissipated by this gap so that the discharge of the recording liquid becomes unstable. Further, in the liquid ejecting recording head for color, an excessive gap is also formed between the first substrate and a common liquid chamber separating wall for separating the common liquid chambers from each other. Therefore, the separation wall of the common liquid chambers becomes insufficient so that the recording liquids of the common liquid chambers are mixed with each other in a worst case.
The reaching position of the liquid droplet is also shifted by slight warping of the second substrate and slight bending of a joining face of the second substrate to the first substrate, etc. caused as the second substrate is large-sized. In particular, when the second substrate is manufactured by injection molding, an important matter is to restrain this slight warping and bending.
Simultaneously, it is gradually required to accurately align the position of a center of the discharging energy generating element of the first substrate and the position of a center of the liquid flow path groove of the second substrate. When these centers are not in conformity with each other, the discharge of the recording liquid is unbalanced and this unbalance has an influence on the reaching position of the liquid droplet. In particular, foaming is unbalanced when the discharging energy generating element is a heating element such as an electricity heat converting element, etc.
In view of the unsolved problems of the above prior art, an object of the present invention is to provide a liquid ejecting recording head in which first and second substrates can be closely joined to each other easily and reliably at low cost and a high definition image can be obtained at high speed.
To achieve the above object, the present invention resides in a liquid ejecting recording head comprising a first substrate in which a discharging energy generating element for generating discharging energy for discharging a recording liquid is formed, a second substrate which has a liquid flow path groove which forms a liquid flow path by joining the liquid flow path groove to the first substrate, a concave portion communicating with the liquid flow path groove and forming a common liquid chamber for temporarily holding the recording liquid, and an orifice plate communicating with the liquid flow path groove and having a discharging port for discharging the recording liquid wherein the liquid ejecting recording head is constructed by joining the first and second substrates to each other in a manner such that the discharging energy generating element and the liquid flow path groove correspond to each other, and both end portions of a pressed face of the second substrate, opposed to a joining face of the second substrate joined to the first substrate, are formed to be thin.
The present invention also resides in a liquid ejecting recording head comprising a first substrate in which a discharging energy generating element for generating discharging energy for discharging a recording liquid is formed, a second substrate which has a liquid flow path groove which forms a liquid flow path by joining the liquid flow path groove to the first substrate, a concave portion communicating with the liquid flow path groove and forming a common liquid chamber for temporarily holding the recording liquid, and an orifice plate communicating with the liquid flow path groove and having a discharging port for discharging the recording liquid wherein the liquid ejecting recording head is constructed by joining the first and second substrates to each other in a manner such that the discharging energy generating element and the liquid flow path groove correspond to each other, and digging-in concave portions are formed in both end portions of a pressed face of the second substrate opposed to a joining face of the second substrate joined to the first substrate.
The present invention also resides in a liquid ejecting recording head comprising a first substrate in which a discharging energy generating element for generating discharging energy for discharging a recording liquid is formed, a second substrate which has a liquid flow path groove which forms a liquid flow path by joining the liquid flow path groove to the first substrate, a concave portion communicating with the liquid flow path groove and forming a common liquid chamber for temporarily holding the recording liquid, and an orifice plate communicating with the liquid flow path groove and having a discharging port for discharging the recording liquid, wherein the liquid ejecting recording head is constructed by joining the first and second substrates to each other in a manner such that the discharging energy generating element and the liquid flow path groove correspond to each other, and a length A of the second substrate in an arranging direction of the liquid flow path groove on a joining face of the second substrate joined to the first substrate is longer than a length B of the first substrate, and is also longer than an arranging length C of the discharging port, and these lengths satisfy the relation of (Axe2x88x92C)/2xe2x89xa71.1 mm and (Bxe2x88x92C)/2xe2x89xa70.825 mm.
The present invention further resides in a liquid ejecting recording head comprising a first substrate in which a discharging energy generating element for generating discharging energy for discharging a recording liquid is formed, a second substrate which has a liquid flow path groove which forms a liquid flow path by joining the liquid flow path groove to the first substrate, a concave portion communicating with the liquid flow path groove and forming a common liquid chamber for temporarily holding the recording liquid, and an orifice plate communicating with the liquid flow path groove and having a discharging port for discharging the recording liquid wherein the liquid ejecting recording head is constructed by joining the first and second substrates to each other in a manner such that the discharging energy generating element and the liquid flow path groove correspond to each other, and at least one concave portion is formed on a face of the orifice plate joined to the first substrate.
In the liquid ejecting recording head of the present invention, digging-in concave portions are preferably formed in both the thin end portions of a pressed face of the second substrate opposed to a joining face of the second substrate joined to the first substrate. Further, both the thin end portions of a pressed face of the second substrate opposed to a joining face of the second substrate joined to the first substrate and the digging-in concave portions are preferably arranged with bilateral symmetry with respect to a central line of the second substrate.
In the liquid ejecting recording head of the present invention, the concave portion formed on the face of the orifice plate is preferably arranged in each of positions corresponding to both end faces of the first substrate.
In the liquid ejecting recording head of the present invention, the concave portion in the second substrate which forms the common liquid chamber by joining the concave portion to the first substrate is preferably separated into plural concave portions by a common liquid chamber separating wall. Further, a concave portion groove preferably extends along a liquid discharging direction, in a portion corresponding to the common liquid chamber separating wall for separating the concave portion forming the common liquid chamber into plural concave portions, on a pressed face of the second substrate opposed to a joining face of the second substrate joined to the first substrate. The concave portion groove can be formed in a trapezoidal shape in cross section.
In accordance with the present invention, warping of the second substrate constituting the liquid ejecting recording head can be reduced. Further, the second substrate is easily deformed and a close attaching property of the second and first substrates can be improved. Thus, the discharging amount and speed of the recording liquid of the liquid ejecting recording head are stabilized. As a result, the reaching accuracy of a recording liquid droplet is improved and a high definition image can be obtained at high speed.
Both end portions of the second substrate on a pressed face of the second substrate opposed to a joining face of the second substrate joined to the first substrate are formed to be thin. Also, a digging-in concave portion is formed in each of the end portions on a pressed face of the second substrate opposed to a joining face of the second substrate joined to the first substrate. Further, a digging-in concave portion is formed in each of the thin wall portions of the end portions. Thus, warping of the second substrate can be reduced and a joining close attaching property can be improved. Further, the molding stability at a molding time of the second substrate can be improved.
Further, a length A of the second substrate in an arranging direction of the liquid flow path groove on a joining face of the second substrate joined to the first substrate is set to be longer than a length B of the first substrate, and is also set to be longer than an arranging length C of the discharging port and these lengths are set to satisfy the relation of (Axe2x88x92C)/2xe2x89xa71.1 mm and (Bxe2x88x92C)/2xe2x89xa70.825 mm. Accordingly, a position of the discharging port for discharging the recording liquid can be separated from the position of a joining start point at which an end portion of the first substrate, as a portion in which stress is concentrated most strongly in pressing and joining of the second substrate to the first substrate, is joined to the second substrate. Therefore, if stress is concentrated, the discharging port is sufficiently separated from this concentrated stress portion that no liquid discharge from the discharging port is influenced by this stress concentration. As a result, when the second substrate and the first substrate are joined to each other by giving a mechanical biasing force, the amount of this biasing force can be increased.
In the orifice plate of the second substrate, at least one concave portion is formed in positions corresponding to both end faces of the first substrate. Accordingly, it is possible to reduce the stress concentration caused when the first and second substrates are joined to each other. Further, deformation of the second substrate can be restrained.